Capsular bag ring and an assembly constituted by such a ring and an injector therefor

ABSTRACT

The invention relates to a ring ( 10 ) for a capsular bag, the ring being constituted by a curved elongate element presenting substantially constant thickness and having inner and outer edges. The elongate element comprises a first branch ( 30 ) extending between a first end ( 20 ) and a point B, and a second branch ( 32 ) extending between said point B and a second end ( 22 ), said outer edge of the elongate element when at rest and in its plane of symmetry being disposed substantially tangentially at a point A to a circle of center O and of radius R not less than the radius of the capsular bag, the outer edge of said first branch being defined by a portion of a circle of center O′ and of radius R′, where R&lt;R′&lt;1.10R, the outer edge of the second branch of said elongate element being defined by a portion of a hyperbolic spiral of center O and connected tangentially to said portion of a circle at said point B.

FIELD OF THE INVENTION

The present invention relates to a capsular bag ring and to an assemblyconstituted by such a ring and an injector therefore.

More precisely, the invention relates to an elastically deformable ringfor putting into place in the capsular bag after removal of the naturallens in order to maintain the natural circular shape of the capsularbag, and particularly but not exclusively in order to make it easysubsequently to put an intraocular implant into place in the capsularbag.

BACKGROUND OF THE INVENTION

It is known that the so-called “cataract” operation consists in removingthe lens while conserving the covering of the lens which is referred toas the capsule or capsular bag. However since the bag is made of a veryfine membrane which is connected to the inside wall of the eye via aring of fibers known as zonules, the membrane tends not to conserve itsregular uniform circular shape.

It is also known that after the lens has been removed, an intraocularimplant is put into place in the capsular bag, which implant consistsessentially in an optical portion of substantially circular shape and anelastically deformable haptic portion which serves to center the opticalportion of the intraocular implant in such a manner that its opticalaxis coincides substantially with the optical axis of the eye. To ensurethat the haptic portions perform their functions adequately, i.e. thatthey hold the optical portion of the implant in a central position, itis necessary for the periphery of the capsular bag, against which thefree ends of the haptic portions press, to retain its circular shape andin particular it is important to avoid folds forming in the capsularbag, so as to avoid complications such as zonules being torn or thecapsular bag shrinking.

To keep the capsular bag in a circular shape, proposals have alreadybeen made to install a resilient ring, usually made ofpolymethylmethacrylate (PMMA) whose elastic expansion serves to keep thecapsular bag circular in shape. As a subsidiary point, the pressureexerted by the ring on the membrane constituting the capsular bag servesto avoid or at least limit the proliferation of parasitic cells that canobscure the capsular bag and thus degrade the patient's vision. Suchcapsular bag rings are described in particular in European patentapplication No. 0 884 031. The ring described therein is symmetrical inshape. That shape does not make it possible to prevent folds forming inthe capsular bag while the ring is being put into place. In addition,that shape does not make it possible to obtain substantially identicalpressure over the entire periphery of the capsular bag.

BACKGROUND OF THE INVENTION

An object of the present invention is to provide a capsular bag ring ofa shape that facilitates insertion into the capsular bag without causingfolds to form therein, and that enables the pressure exerted by the ringon the periphery of the capsular bag to be distributed better and thusmore effectively so as to further improve maintenance of the naturalcircular shape of said capsular bag.

To achieve this object, the invention provides a capsular bag ringconstituted by a curved elongate element presenting a first end and asecond end provided with handling means, said elongate elementpresenting a plane of symmetry, thickness that is substantially constantin a direction orthogonal to said plane of symmetry, and inner and outeredges, said outer edge of the elongate element when at rest and in itsplane of symmetry being disposed substantially tangentially at a point Ato a circle of center O and of radius R that is not less than the radiusof the capsular bag, said outer edge being located at the outside ofsaid circle, said ring being characterized in that said elongate elementfurther comprises a first branch extending between said first end and apoint B, and a second branch extending between said point B and saidsecond end, said elongate element being of a length that issubstantially not less than the length of the perimeter of said circleof center O, the outer edge of said first branch being defined by aportion of a circle of center O′ and of radius R′, where R<R′<1.10R, andin that the outer edge of the second branch of said elongate element isdefined by a portion of a hyperbolic spiral of center O and joiningtangentially with said portion of a circle at said point B, close tosaid tangential point A, whereby:

the length of any segment joining the center O to a point M′ of theouter edge of the second branch is greater than the length of thesegment joining the center O of the circle to a point M′ of the outeredge of the first branch, the point M being such that the angle betweenthe segment OM and the median diameter joining the center O to thetangential point A is equal to the angle between the segment OM′ andsaid median diameter; and

the radius of curvature at any point M′ of the outer edge of the secondbranch is greater than the radius R′.

It will be understood that the ring comprises a first branchsubstantially in the shape of a circular arc whose radius is slightlygreater than that of the capsular bag and a second branch in the form ofa portion of a hyperbolic spiral. The first branch is the branch that isinserted first into the capsular bag. Because this branch correspondsmore or less to a semicircle of radius close to that of the capsularbag, it is easy to put this first branch into place in the capsular bag.It is only when the second branch of spiral shape is introduced into thecapsular bag that the ring is subjected to significant elasticdeformation of its second branch. In addition, because of its hyperbolicspiral shape, the extra diameter of the ring in said second branchcompared with the diameter of the capsular bag increases onlyprogressively. This makes it easier to put the second branch of the ringinto place and thus to put the entire ring into place, since the secondbranch is compressed progressively.

In addition, since the elastic deformation of the ring which serves tokeep the capsular bag in shape is distributed along the second branch ofthe ring which corresponds substantially to a semicircle, distributionof the stresses applied to the capsular bag is encouraged, therebyavoiding the risk of folds forming in said bag.

Another problem which arises is that of how to insert the ring insidethe eye and the capsular bag. To do this, it is known to use an injectorwhich is terminated by a cannula of small diameter so as to enable it tobe inserted into the eye through an incision of small size, typicallyabout 2.5 millimeters (mm) to 4 mm. The ring of the capsular bag has anorifice at at least one of its ends suitable for receiving a hook fixedto the end of a wire which enables the entire ring to be inserted insidethe cannula and subsequently ejected from the cannula once the end ofthe cannula is inserted in the eye. Putting the end of the ring intoplace on the hook of the injector requires a certain amount of handlingwhich is quite difficult because of the small dimensions of the ring andof the hook at the end of the injector wire.

There therefore exists a real problem relating to putting the capsularbag ring into place inside the injector in order to enable it to beinserted into the eye.

Another object of the invention is to provide a system comprising acapsular bag ring associated with an injector to avoid theabove-mentioned prior handling.

The capsular bag ring system is characterized in that it comprises:

a capsular bag ring comprising two asymmetrical branches presentingdifferent radii of curvature; and

a ring injector for putting said ring into place in the capsular bag,said injector comprising:

a cannula provided with an axial passage;

a body provided with a ring-handling mechanism, said mechanismcomprising a flexible wire engaged in said axial passage, said wirehaving a first end provided with a handling member suitable forco-operating with the handling means of the ring to secure said wiretemporarily to said ring, and a second end secured to means for movingsaid wire in said passage; and

in that when said handling member is secured to said handling means,said ring is engaged in the axial passage of said cannula via its secondend over a suitable length of its second branch without applying anystress to the branch.

It will be understood that because, in accordance with the invention,the branch of the ring that is inserted in part into the cannulapresents a radius of curvature that is much greater than that which isto be found in prior art rings, it is possible to insert one end of saidbranch into the cannula of the injector and to store the assembly untilit is used by a surgeon.

Because of this large radius of curvature, the end of the second branchof the ring can remain stored in the cannula without that impartingsignificant deformation to the branch of the ring. It should beemphasized that such a disposition is not possible with standard typerings since the ends thereof present significant curvature which wouldgive rise to stresses in the corresponding end of the ring likely toreduce its strength significantly after being stored for a certainlength of time.

Other characteristics and advantages of the invention will appear betteron reading the following description of various embodiments of theinvention given as non-limiting examples. The description refers to theaccompanying figures, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a capsular bag ring of the invention;

FIG. 2 is a longitudinal section view of a first embodiment of a ringinjector;

FIGS. 3A and 3B are views in perspective and partially in sectionshowing a portion of the FIG. 2 injector that enables it to be locked;

FIG. 4 is a fragmentary longitudinal section view showing the ring beingput into place in the cannula of the injector;

FIG. 5 is a view showing a detail of FIG. 4, showing the position of theend of the ring inside the cannula;

FIG. 6 shows an embodiment of the member for securing the ring to thecannula;

FIG. 7 is a longitudinal section view of a second embodiment of theinjector;

FIG. 7A is a section view on line A—A of FIG. 7; and

FIG. 7B is a fragmentary perspective view of the FIG. 7 injector.

DETAILED DESCRIPTION OF THE INVENTION

With reference initially to FIG. 1, a capsular ring of the invention isdescribed in its rest shape, i.e. the shape it takes up when no stressis applied thereto. It is preferably made of PMMA which is a materialthat is biocompatible and in widespread use for making intraocularimplants, and in particular for making the haptic portions of suchimplants.

The ring 10 can be defined relative to a circle C of center O and radiusR, said radius being substantially equal to the radius of the capsularbag in which the ring is to be installed. The ring 10 is tangential tothe outside of the circle C at a point A. More precisely, the circle Cis tangential to the outer edge 12 of the ring 10, said ring also havingan inner edge 14. The ring is in the form of an elongate piece having afirst end 16 and a second end 18. In this embodiment, the width of thering, i.e. the distance between the edges 12 and 14 is constant. By wayof example it can be equal to 0.17 mm. The thickness of the ring in adirection perpendicular to its plane of symmetry is substantiallyconstant. For example it can be equal to 0.17 mm. Only the terminalportions 20 and 22 corresponding to the ends 16 and 18 are of increasedwidth so as to make it possible to form holes 24 and 26 for handling thering. The term “main” portion of the ring is used to designate itsentire length with the exception of its terminal portions 20 and 22.

Returning to defining the shape of the ring, it has a first branch 30extending from its first end 16 to a point B of the outer edge, saidpoint B being offset from the tangential point A by an angle at thecenter of the circle C which is equal to b. The angle at the center bpreferably lies in the range 1° to 15°, and the point B is situated onthe same side of the median diameter AA′ as is the second branch. Thering has a second branch 32 which extends from the point B to the secondend of the ring 18.

The first branch 30 is general in the shape of a portion of a circle 34of center O′ and radius R′, the center O′ generally not coinciding withthe center O of the circle C. The radius R′ lies in the range R to R+10%of R. Relative to the center O′ of the circular arc 34, the angle at thecenter a subtended by said circular arc at the point O′ is less than180°, and preferably greater than 120°.

It will be understood that the first branch 30 of the ring is generallyin the form of a circular arc that is slightly smaller than a semicircleand that has a radius R′ that is slightly greater than the radius of thecapsular bag.

The outer edge 12 of the second branch 32 of the ring is defined by ahyperbolic spiral, or more precisely, by a portion of a hyperbolicspiral of center O. In the particular embodiment shown, the equation forthe portion of a spiral in polar coordinates is r=17/q where q is theangle at the center.

Because of the shape of the branches 30 and 32 of the ring, it will beunderstood that when considering a point M′ on the outer edge of thesecond branch 32 making an angle x with the median diameter AA′ of thecircle C and also considering the point M on the outer edge of the firstbranch 30 that makes the same angle x with the diameter AA′, then thedistance OM′ is always greater than the distance OM. It will also beunderstood that the radius of curvature of the second branch 32 is muchgreater than the radius of curvature of the first branch, with saidradius of curvature increasing on going away from the point B towardsthe second end 18 of the ring.

For the reasons described above relating to the shapes of the twobranches of the ring, it will be understood that the ring can easily beput into place in the capsular bag.

FIG. 2 shows a ring injector 40. The injector comprises a cylindricalbody 42 terminating in a conical portion 44 having a cannula fixedthereto, which cannula is in the shape of a circular arc 46. A piston 48can move inside the body 42, the piston having a manual actuation head50 and a second end 52 which is secured to the end of a wire 54 whichcan move inside the cannula 46 when the piston 48 moves. As explained ingreater detail below, the wire 54 is terminated by a hook 56 enablingthe second end 18 of the ring to be secured thereto because of thepresence of the handling hole 26. A return spring 58 interposed betweena shoulder 60 of the piston 48 and a shoulder 62 of the body of theinjector tends to draw the wire 54 into the cannula 46. For reasonsexplained below, the injector 40 is preferably fitted with a removableclip-forming piece 64 including a stud 66 which can be engaged in holes68 in the body of the injector and in a bore 70 in the piston 48 of theinjector. When the piece 64 is in place, the piston 48 and thus the hookon the wire 54 of the injector are held stationary in a precise positionwhich is set back by a length l from the opening 46 a of the cannula.

FIG. 4 shows the injector 40 fitted with a capsular bag ring 10 whosesecond end 18 penetrates through the end of the cannula and is securedto the wire 54 by means of the hook 56. As can be seen more clearly inFIG. 5, the second end of the second branch 32 of the ring 10 penetratesinto the cannula 46 over a length l which is such that the end of thering can be housed without any significant stress being applied thereto.As already explained, this particularly favorable result is obtainedbecause the radius of curvature of the second end of the second branch32 of the ring is much greater than that which is to be found incapsular bag rings of the state of the art.

The length l preferably lies in the range 4 mm to 5 mm.

FIG. 6 shows a preferred embodiment of the hook 56 on the wire 54 of theinjector in greater detail. It is constituted by an angled end portionof the wire. The angle c made by the angled portion relative to the mainportion of the wire lies in the range 45° to 90°. It will be understoodthat because of the shape of the hook, it is held inside the hole 26 ofthe ring so long as the end of the ring remains inside the cannula 46.When this end is extracted therefrom, merely by moving the injector, thesurgeon can separate the ring from the injector.

In a preferred embodiment, the cannula has an internal bore ofelliptical section having axes of lengths 1.1 mm and 0.6 mm. The wire 54has a diameter of 0.3 mm and the hole 26 has a diameter of 0.4 mm.

It will be understood that because no stress is applied to the end ofthe ring, the assembly constituted by the injector together with thering 10 having its second end engaged inside the cannula of the injectorand connected to the wire 54 of said injector can be stored for a longperiod of time. The assembly is placed in a pack that presents relativesealing that allows gas (ethylene oxide) to pass through for the purposeof sterilizing the assembly constituted by the injector and the ring.

Thus, when the surgeon seeks to put the ring into place in the capsularbag of a patient, the ring is already connected to the wire 54 of theinjector. All the surgeon needs to do is to remove the clip-formingpiece 64 and then the piston 48 moves rearwards under drive from thereturn spring causing the entire ring 10 to be drawn into the cannula46. The surgeon then inserts the end 46 a of the cannula into thepatient's eye through the incision that has already been made, whereuponit suffices to press the piston so as to cause the ring to be expelledprogressively, with the ring penetrating little by little into thecapsular bag, beginning with its first branch which, as alreadyexplained, is substantially in the form of a semicircle correspondingsubstantially to the natural shape of the periphery of the capsular bag.

FIGS. 7, 7A, and 7B show a second embodiment of the injector. Thisembodiment comprises a cylindrical hollow body 70 in which a piston 72can move. The conical end 74 of the body 70 is fitted with a cannula 76identical to the cannula 46 of FIG. 2. A return spring 78 urges thepiston 72 away from the frustoconical end 74. A hook wire 80 is securedto the end 72 a and can move inside the cannula 76.

The piston 72 has an annular groove 82 receiving a displacement member84 constituted by a split ring 86 engaged in the groove 82 and by adisplacement finger 88. The finger 88 is thus constrained to move intranslation with the piston 72 but is free to rotate. The finger 88penetrates into a slot 90 formed in the body 72 of the injector. Theshape of the slot 90 can be seen more clearly in FIG. 7B. This slot hasa rectilinear portion 92 parallel to the axis of the injector body and adeflected portion 94. The rectilinear portion 92 extends between a pointE close to the frustoconical end and a point F (FIG. 7). When the finger88 is in the position E, the wire 80 is fully extended from the cannulaand the ring can be detached from the wire. When the finger 88 is in theposition F, all of the ring is inside the cannula 76. This is theinitial position for insertion.

The deflected portion 94 of the slot defines the storage position. Theportion 94 of the slot comprises a first branch 96 extending betweenpoints G and H, the point G corresponding to the storage position of thering in which only a very small portion of the ring is received insidethe cannula as described above. The second branch 98 extends from thepoint H to a point I which connects with the rectilinear slot 92.

In the storage position, the finger 88 is held in stable manner in theposition G under thrust from the spring 78 because of the bendconstituted by the point H.

When the surgeon seeks to use the injector, it is necessary to applypressure to the head of the piston 72 until the finger 88 has gone pastthe bend H in the diverted slot 94. From this position, under drive fromthe spring 78, the finger 88 follows the slot portion 96 and then therectilinear slot 92 until it reaches the point F. The ring is then fullyengaged inside the cannula. The assembly is ready for injecting thering.

The surgeon then need only apply pressure to the head of the piston 72in order to cause the ring to be ejected progressively from the cannulaof the injector, with the finger 88 traveling along the rectilinear slot92.

When the finger 88 reaches the point E, the ring is fully in place inthe patient's eye and can be unhooked from the end of the wire 80.

What is claimed is:
 1. A capsular bag ring to be implanted within thecapsular bag of an eye, the capsular bag denoting a circle having acenter O, a radius R and a tangential point A, said ring comprising anelongate element forming two asymmetrical branches having differentradii of curvature, each branch of said element beginning at aconnection point B and terminating in first and second endsrespectively, each of said end having handling means, a first branchextending between said first end and said connection point B, and asecond branch extending between said point B and said second end, saidbranches of said element lying in a plane and having a thickness that isconstant in a direction that is orthogonal to said plane and saidelement having inner and outer edges, said elongate element having alength greater than the perimeter of said circle of said capsular bagand said outer edge of said first branch defining a portion of a circleof the center O′ and radius R′, where R<R′<1.10R, the outer edge of saidelongate element defining a portion of a hyperbolic spiral of saidcenter O and joining tangentially with said portion of said circle ofcenter O′ at said connection point B, whereby, a length of any segmentjoining the center O to a point M′ of the outer edge of the secondbranch is greater than the length of a corresponding segment joining thecenter O of the circle to a point M′ of the outer edge of the firstbranch, the point M being such that the angle between the segment OM anda median diameter joining the center O to a tangential point A is equalto the angle between the segment OM′ and said median diameter; andwherein the radius of curvature at a point M′ of the outer edge of thesecond branch is greater than the R′.
 2. A ring according to claim 1,wherein at least said second end of said elongate element presents aterminal portion in said plane of symmetry that is of increased width,and wherein said handling means comprise a handling hole provided insaid portion.
 3. A ring according to claim 1, wherein said connectionpoint B between said two branches is located on the same side of themedian diameter as is said second branch.
 4. A ring according to claim1, wherein said elongate element is of substantially constant widthbetween said inner and outer edges in its main portion.
 5. A ringaccording to claim 1, including an angle (a), the apex of which is O′,and corresponding to said first branch, is less than 180° and greaterthan 120°.
 6. A ring according to claim 1, wherein said ring is made ofPMMA.
 7. A capsular bag ring system, comprising: a capsular bag ringcomprising an elongate element forming two asymmetrical branches havingdifferent radii of curvature, each branch of said element beginning at aconnection point B and terminating in first and second endsrespectively, each of said end having first securing means; and a ringinjector for implanting said ring into a capsular bag of the eye, saidinjector comprising: a cannula having an axial passage; a body having aring handling mechanism, said mechanism comprising a flexible wireengaged in said axial passage, said wire having a first end providedwith second securing means suitable for engaging with said firstsecuring means of the ring to secure said wire to said ring forimplantation of the ring into the eye and insertion of the ring intosaid cannula, and a second end; and moving means connected to saidsecond end of said wire for moving said wire in said cannula, wherebywhen said first securing means are secured to said second securingmeans, said ring can be maintained partially engaged in said axialpassage of said cannula.
 8. A ring system according to claim 7, furthercomprising a package containing said injector and said ring engaged insaid cannula.
 9. A ring system according to claim 8, wherein saidpackage is made of a material that enables sterilization to be performedby means of a gas.
 10. A capsular bag ring system, comprising: acapsular bag ring comprising an elongate element forming twoasymmetrical branches having different radii of curvature, each branchof said element beginning at a connection point B and terminating infirst and second ends respectively, each of said end having a hole; anda ring injector for implanting said ring into a capsular bag of the eye,said injector comprising: a cannula having an axial passage; a bodyhaving a ring handling mechanism, said mechanism comprising a flexiblewire engaged in said axial passage, said wire having a first endprovided with a hook suitable for engaging with said hole of the ring tosecure said wire to said ring for implantation of the ring into the eyeand insertion of the ring into said cannula, and a second end; andmoving means connected to said second end of said wire for moving saidwire in said cannula, whereby when said hole is secured to said hook,said ring can be maintained partially engaged in said axial passage ofsaid cannula.